Blood samples from 9-year-olds can predict bipolar symptoms

High anxiety? Manic behaviour may start with inflammation in childhood

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By Helen Thomson

High levels of inflammation as a child may predict a higher risk of manic behaviour in later life, a finding that could lead to new ways of treating conditions like bipolar disorder.

Hypomania involves spells of hyperactivity and is often a symptom of mood disorders, including bipolar disorder, seasonal affective disorder and some kinds of psychosis. People experiencing hypomania may take more risks, feel more confident and become impatient with others. After spells like this, they may “crash”, needing to sleep for long periods and sometimes remembering little about the previous few days.

Earlier studies suggested a link between inflammation and mood disorders, prompting Joseph Hayes at University College London and his team to see if inflammation as a child might lead to mental health problems later.

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Analysing data from more than 1700 people, his team identified a significant link between high levels of a chemical involved in inflammation at age 9, and experiencing aspects of hypomania at age 22.

Brain changes

The chemical, called IL-6, is normally secreted by white blood cells to stimulate an inflammatory immune response to infection or trauma. Hayes’s team says it is unclear how inflammation in childhood could induce symptoms of hypomania but IL-6 is known to affect the brain. A study that used injections to increase IL-6 in the blood of healthy volunteers found that this caused symptoms of anxiety, and reduced performance in memory tests.

The team suggests that targeting inflammatory pathways may help treat conditions such as bipolar disorder.

“The study provides important new evidence in support of a role for inflammation in pathological increases in mood,” says Neil Harrison at Brighton & Sussex Medical School in the UK. “Taken together with results from earlier studies, this suggests that high levels of inflammation during childhood increase the risk of disorders of mood later in life.”